1. Field of the Invention
The present invention relates to angular contact linear slide bearings of the type which is suitable for use in linearly guiding movable elements in slide portions of industrial robots or machine tools such as numerical control machines.
2. Description of the Prior Art
As is well known, such an angular contact linear slide bearing comprises a bearing block including a pair of ball rolling surfaces formed adjacent to each other and unloaded ball passages each formed in opposing relationship with a corresponding one of the ball rolling surfaces, end caps mounted to the respective ones of the opposite end surfaces of the bearing block for providing communication between the opposite ends of each of the ball rolling surfaces and the opposite ends of the corresponding one of the unloaded ball passages to thereby form a pair of endless tracks, a multiplicity of balls which roll along each of the endless tracks, and a track rail having a pair of ball rolling grooves along which the balls roll in a loaded state while they are rolling on the ball rolling surfaces of the bearing block. In use, one angular contact linear slide bearing is mounted to, for example, each of opposite sides of a table, and these two bearings are made to support in combination four-directional loads of radial loads, reverse-radial loads, rightward loads and leftward loads.
In such an angular contact linear slide bearing, a ball retainer including a pair of slots each having a slightly smaller width than the diameter of each ball is mounted on the portion defined between the end caps in such a manner that each of the slots is positioned parallel to the corresponding one of the ball rolling surfaces of the bearing block. In this arrangement, the balls are prevented from coming off while they are rolling on the ball rolling surfaces of the bearing block, and it is possible to improve the working efficiency when bearings are to be incorporated into a table or the like.
The above-described angular contact linear slide bearing can be used to constitute a linear guide mechanism which is compact in size and stable owing to its low center of gravity. In addition, the angular contact linear slide bearing possesses various other advantages; for example, clearance adjustment is easy, rigidity can be built up by increasing preload, and light sliding motion can be achieved by reducing preload.
However, in the above-described conventional type of angular contact linear slide bearing, the ball retainer is commonly formed by pressing a metal sheet having a small sheet thickness, and also, the slots are formed substantially over the entire length of the ball retainer. The ball retainer is only secured at its opposite ends to a pair of end caps. For this reason, the ball retainer is particularly susceptible to twisting, and is easily deformed owing to a lack of the strength and rigidity of the ball retainer itself. As a result, the ball retainer is liable to curve or the width of each slot may change, and therefore it is difficult to precisely work the ball retainer. Even if the ball retainer can be precisely worked, the dimensions thereof are easily changed due to deformation, and, during use, the deformed ball retainer may contact with rolling balls, so that noise is generated or smooth sliding motion is hindered. In addition, the ball retainer and the end caps must be manually mounted to the bearing block since these four components need to be accurately positioned with respect to one another. This leads to the problem that the automation of bearing assembly is difficult.